Second order intermodulation distortion (IM2) in mixers is caused by self mixing within the mixer.
Second order components from the self mixing are within low frequency bands where they can superpose desired signals and can therefore aggravate subsequent signal processing.
Some mixers, such as Gilbert-type mixers, have a differential output such that IM2 exists as a removable common-mode signal when both individual output paths are identical. However, due to duty-cycle errors as a consequence of mismatches in the switching transistors, the IM2 in the common mode of the RF-input transistors leaks into the differential mode at the mixer output.
It is object of the present invention to provide a mixer which reduces second order distortion, or at least provides a useful alternative.